This invention relates to the hydroformylation and hydrogenation synthesis of an aliphatic 1,3-diol, particularly 1,3-propanediol, from an oxirane, especially ethylene oxide (hereafter EO), and syngas in one step using a catalyst system comprised of cobalt carbonyl and a ligand.
Aliphatic 1,3-diols, particularly 1,3-propanediol, have many applications as monomer units for polyester and polyurethane, and as starting materials for the synthesis of cyclic compounds. For example, CORTERRA(copyright) polytrimethylene terephthalate is a polyester characterized by outstanding properties that is made of 1,3-propanediol (hereafter PDO) and terephthalic acid. There is much interest in the art in finding new routes for synthesizing PDO that are efficient, economical, and demonstrate process advantages.
U.S. Pat. Nos. 3,463,819 and 3,456,017 teach the hydroformylation of ethylene oxide to produce 1,3-propanediol and 3-hydroxypropanal (hereafter HPA) using a tertiary phosphine-modified cobalt carbonyl catalyst. U.S. Pat. Nos. 5,256,827; 5,344,993; 5,459,299; 5,463,144; 5,463,145; 5,463,146; 5,545,765; 5,545,766; 5,545,767; and, 5,563,302, 5,689,016, all assigned to Shell Oil Company, disclose cobalt catalyzed hydroformylation of ethylene oxide.
U.S. Pat. No. 5,304,691, assigned to Shell Oil Company, discloses a method of hydroformylating ethylene oxide to 3-hydroxypropanal and 1,3-propanediol in a single step using an improved catalyst system comprising a cobalt-tertiary phosphine ligand in combination with a ruthenium catalyst. In ""691 PDO and HPA are produced by intimately contacting an oxirane, particularly ethylene oxide (EO), a ditertiary phosphine-modified cobalt carbonyl catalyst, a ruthenium co-catalyst, and syngas (carbon monoxide and hydrogen) in an inert reaction solvent at hydroformylation reaction conditions. A PDO yield of up to 86-87 mole % is reported, using a catalyst comprising cobalt ligated with 1,2-bis (9-phosphabicyclononyl) ethane as bidentate ligand, and either triruthenium (0) dodecacarbonyl or bis[ruthenium tricarbonyl dichloride] as cocatalyst. Also see U.S. Pat. No. 5,304,686, assigned to Shell, which discloses the synthesis of 3-hydroxypropanal using a ditertiary phosphine-modified cobalt carbonyl catalyst and a catalyst promoter. In the aforementioned patents, where a phosphine ligand is employed, it is bound to cobalt carbonyl.
It is known that water extraction can recover HPA intermediate or PDO product from an non-water-soluble solvent system in a two-step process and that use of a lipophilic promoter (quaternary ammonium or phosphonium, or lipophilic amine) rather than a sodium salt allows a majority of the cobalt carbonyl catalyst to recycle with the organic solvent phase, as desired. See, for example, U.S. Pat. Nos. 5,463,144; 5,463,145; 5,463,146; 5,545,765; 5,545,766; 5,545,767; 5,563,302; 5,576,471; 5,585,528; 5,684,214; 5,689,016; 5,731,478; 5,723,389; 5,770,776; 5,777,182; 5,786,524; and 5,841,003, all assigned to Shell.
Copending commonly assigned U.S. patent application Ser. Nos. 09/808,974 and 09/963,068 disclose, inter alia, phosphine ligated bimetallic catalyst compositions useful in the one-step synthesis of PDO, and a process for one-step synthesis of PDO. In these references the phosphine ligands are bound to the ruthenium compound rather than the cobalt compound.
Ruthenium carbonyls modified with phosphine ligands are quite effective as catalyst complexes in the one-step synthesis of PDO. However, phosphine ligands are relatively expensive and, in some cases, catalyst recycle may fall short of optimal. At the same time, product selectivity may fall short upon repeated recycle. These observations have thus far made it rather prohibitive to use phosphine ligands in hydroformylation catalysts for commercial use. It would be extremely desirable if substantially less ligand were effective in a bimetallic catalyst complex for the one-step synthesis of PDO and if other modifications, such as water extraction, enhanced the use of a reduced ratio and contributed to efficient recycle.
In accordance with the foregoing, the present invention is a process for hydroformylating and hydrogenating oxiranes, especially ethylene oxide, carbon monoxide, and hydrogen to produce aliphatic 1,3-diols, especially PDO, in one step where recovery of product is accomplished via aqueous extraction, preferably with water, of a diol rich phase from the bulk reaction liquor. The preferred process comprises the steps of:
(a) Contacting at a temperature within the range from about 30 to about 150xc2x0 C. and a pressure within the range of about 3 to about 25 MPa, an oxirane, particularly ethylene oxide, carbon monoxide, and hydrogen, in an essentially non-water-miscible solvent in the presence of an effective amount of a homogeneous bimetallic hydroformylation catalyst comprising a cobalt carbonyl compound, preferably an essentially non-ligated cobalt carbonyl compound, and a cocatalyst metal, which is selected from ruthenium, copper, platinum, and palladium, and which is ligated with a ligand selected from a phosphine ligand, a bidentate or multidentate N-heterocyclic ligand, a porphorine ligand, and a phospholanoalkane ligand, optionally in the presence of a promoter, preferably a lipophilic promoter, wherein the molar ratio of ligand to cocatalyst metal atom may vary from about 0.2:1.0 to about 0.6:1.0, preferably about 0.20:1.0 to about 0.40:1.0, under reaction conditions effective to produce a reaction product mixture containing an aliphatic 1,3-diol such as PDO;
(b) Adding an aqueous liquid to said reaction product mixture and extracting into said aqueous liquid a major portion of the 1,3-diol (PDO) at a temperature less than about 100xc2x0 C. to provide an aqueous phase comprising the 1,3-diol (PDO) in greater concentration than the concentration of 1,3-diol (PDO) in the reaction product mixture and an organic phase comprising at least a portion of the bimetallic hydroformylation catalyst and preferably any promoter;
(c) Separating the aqueous phase from the organic phase; and
(d) Optionally but preferably returning at least a portion of the organic phase containing catalyst to step (a).
This invention relates to modifications of said one-step process for synthesizing aliphatic 1,3-diols, especially PDO, which comprise: a) employing 4- to 5-fold less ligand at lower ligand/cocatalyst metal ratios than previously thought effective; and b) employing water extraction to recover product and recycle catalyst. These modifications offer a significant economic advantage, as the use of reduced ligand offers the potential to substantially reduce ligand usage and cost, while water extraction allows recycle of a majority of catalyst with the solvent phase with -reduced thermal degradation.